1. Field of the Invention
The present invention relates to a shape measuring instrument, an impedance detector, and an impedance detection method. For example, the present invention relates to a shape measuring instrument, an impedance detector, and an impedance detection method that detect impedance in a cable having a bent portion and connected to a movable portion.
2. Description of Related Art
Nowadays, in order to test accuracy of processing on a manufactured item having a three-dimensional shape, a shape measurer such as a coordinate measuring device is used. A coordinate measuring device of this kind performs shape measurement by displacing a probe mounted on a non-contact measurer along the three-dimensional shape. When such shape measurement is conducted for a long period of time, impedance increases due to repeatedly bending a cable connected to the probe. The cable is chiefly configured by electric wires made of metal. When metal having a high degree of purity is repeatedly deformed within its range of elastic deformation, no distortion is caused in a metallic crystalline structure thereof. However, in an actual cable, when deformation is repeated a large number of times, even within the range of elastic deformation, distortion gradually accrues, caused by the metallic crystalline structure, which contains impurities. As a result, impedance in the cable increases. For example, in a coordinate measuring device that transfers image data, data transfer becomes impossible due to the increased impedance in the cable.
In order to resolve the above-noted issues, a technique has been suggested in which impedance is reviewed by a signal wire conduction check in a case where a contact measurer is mounted on a probe (Japanese Patent Laid-open Publication No. 2007-333674). The technique discloses performing the impedance review using a dedicated testing tool.
However, the inventor of the present invention has discovered an issue with respect to the above-noted technique. The above-noted technique requires the dedicated testing tool. Therefore, the impedance review cannot be performed readily, which causes costs to increase.